Ceramic Engine Parts: Piston Coating & Beyond

[wolram]

Some years ago i read of an attempt to make major engine componets from ceramics, i see now that ceramic coating is available for some parts (piston), so what is preventing the use of ceramics for say an engine block
or cylinder head?

 

[Danger]

I'm not sure about this, Woolie, but I'm under the impression that ceramics of that sort are heavier than aluminum. If that's the case, then making a block or heads out of them would be counter-productive.

 

[Hawknc]

Also I would think that a ceramic cylinder head would be more difficult to lubricate and/or seal, but that's just from my admittedly limited understanding of ceramics.

 

[GENIERE]

… ceramics of that sort are heavier than aluminum. If that's the case, then making a block or heads out of them would be counter-productive.

Not so counterproductive as you may think. The desirability of the ceramic engine lies on it being able to operate more efficiently at high temperatures, perhaps without an energy wasting cooling system.

 

[wolram]

http://www.ceramicrotaryengines.com/

Reaserch into ceramic engine/parts/coatings.

 

[Clausius2]

At the time I heard about this, the problem with ceramic cylinders was the Fracture. Ceramic is a fragil material, but it can withstand higher temperatures and reduce heat losses.

 

[wolram]

At the time I heard about this, the problem with ceramic cylinders was the Fracture. Ceramic is a fragil material, but it can withstand higher temperatures and reduce heat losses.

That is true Clausius, but there is work in progress to eliminate this problem.

http://www.mse.ntu.edu.sg/research/?op=defence/components.html

 

[FredGarvin]

We are lookng at using ceramic turbines in an attempt to increase allowable inlet temps. They have a very wide array of technical hurdles to overcome in a rotating frame. I can just imagine there would be a separate set of difficulties with a recip.

 

[Q_Goest]

When I was in college 20 years ago, ceramic coatings for IC engines was all the rage. Folks were thinking they were just a few years away from becoming reality.

The benefits are pretty obvious, higher internal engine temperatures means less heat loss and higher efficiency, yet in 20 years they still haven't made any significant impact.

The problem with the coatings cracking and shedding particles is one significant problem and I suppose putting them on cylinder walls is a huge technical challenge. I wonder though if part of the issue isn't also economic. Perhaps they just aren't seen as being economic enough to warrent their application. If that's the case, higher gas prices may change that, but in Europe the gas prices have been high for decades.

I guess I don't know why ceramics aren't used in engines!

 

[wolram]

When I was in college 20 years ago, ceramic coatings for IC engines was all the rage. Folks were thinking they were just a few years away from becoming reality.

The benefits are pretty obvious, higher internal engine temperatures means less heat loss and higher efficiency, yet in 20 years they still haven't made any significant impact.

The problem with the coatings cracking and shedding particles is one significant problem and I suppose putting them on cylinder walls is a huge technical challenge. I wonder though if part of the issue isn't also economic. Perhaps they just aren't seen as being economic enough to warrent their application. If that's the case, higher gas prices may change that, but in Europe the gas prices have been high for decades.

I guess I don't know why ceramics aren't used in engines!

Cylinders coating has been around for a while Q.

http://www.poeton.co.uk/w1/a2000.htm

 

[brewnog]

Cracking, cost, and thermal expansion differences are all issues, there's not much going on in the way of ceramic engine core component research these days. Big advances in ceramics are being made in areas like turbomachinery, - rotating inertia of a turbine can be something like 70% less than with conventional materials, which dramatically increases load acceptance and slashes turbo lag.

 

[Aysee]

Ceramic materials are very brittle and generally has a significantly low toughness values according to the metals. Also weibull modulus of the ceramic materials are not as high as metals thus their reliability is limited. But there are many investigations on these materials to produce engine parts as a monolithic ceramic material or as a composite material by the aid of a metal reinforcement.

 

[xxChrisxx]

Well I never would have expected investigating ceramics for turbomachinery. Yes it can pretty much solve the heat problem but I would have thought they would have been crap when rotating due to the vibration and low fracture toughness.

Im going to have to read up on this :)

 

[mgb_phys]

Would the extra thermodynamic efficency of higher temperatures make up for all the extra effort you are going to need to remove all the extra NOx produced at higher T ?

 

[Topher925]

It should be noted that with the Otto cycle, temperature does not necessarily relate to high efficiencies as it does with the Brayton cycle. The purpose of using materials that can withstand higher temperatures is to achieve higher compression ratios which are currently limited by material's maximum operating temps.

I think the extra NOx production could be offset by a more robust catalytic converter. It wouldn't hinder performance but would certainly increase cost. I know turbine engine manufacturers have been trying to use ceramic blades for decades but the biggest issue is with reliability from fatigue. I guess ceramics just don't behave as well as metal alloys when it comes to reliability standards.

 

[brewnog]

Would the extra thermodynamic efficency of higher temperatures make up for all the extra effort you are going to need to remove all the extra NOx produced at higher T ?

You possibly wouldn't see a big increase in peak cylinder temperatures. Mean cylinder temperatures (more importantly piston crown temperatures) may go up a fair amount (giving you your thermodynamic efficiency benefit) without pushing peak temperatures (where your NOx is formed) up much.

 

[dbowser]

Does anyone have thoughts about the injection of water in this context? In discussing with some of the lead mechanical engineers at a large engine research lab (I was in a lead software position there at the time) about water injection, the only issue they came up with was corrosion. When I asked if that could be addressed by ceramic parts they wouldn't answer. It seems that this would allow for dramatic reclamation of the thermal energy that is normally lost in the combustion cycle and thus huge gains in engine efficiency.

 

[minger]

Well I never would have expected investigating ceramics for turbomachinery. Yes it can pretty much solve the heat problem but I would have thought they would have been crap when rotating due to the vibration and low fracture toughness.

Im going to have to read up on this :)

Can't believe this thread got resurrected twice, but what the hell, I'll chime in.

Ceramics for turbomachinery, while there are quite a few associated problems, are well worth the trouble. As Fred mentioned, allowing higher inlet and combustor temps can greatly increase effiiciencies and output; one often uses impingment or some other bleed air just to cool it down.

There are a few hurdles though. As you mentioned vibration is somewhat of an issue, although not as much as you might expect. Gas turbine shafts are balanced EXTREMELY well, so as long as one isn't running at a critical speed, vibration is expected to be minimal.

One issue is actually making the part. As you might imagine, ceramics are rather hard to make, and don't take to machining particularly well. One other poster mentioned weight. Actually ceramics are very light. Looking at some materials that I'm familar with, silicon nitride is only like 10% heavier than A356 aluminum.

One problem that is one of the biggest ones that I know of it attachment. How do you want to attach a ceramic turbine to a metal shaft? You really can't put holes in it to bolt, and you certainly can't weld/braze it. I have seen one or two decent solutions, but it's still extremely tricky.

 

[dr dodge]

I know this thing is not ceramic, but
I had followed the development of this for years, (in PS) and I think (but couldn't find the article) that they eventually used ceramic coatings on the piston and head

http://books.google.com/books?id=FzCnbu4xM0YC&pg=PA71&dq=plastic+engine&as_brr=1&cd=1#

This almost needs to go in the historical engine thread, too

dr